Re: Updated WOFF2 spec is available for review

For empty glyphs, it should probably point to the *next* record or take the
value numGlyphs+1 if this is the last glyph. Adjusting n-1 to have the same
offset as n would denote n-1 as empty rather than marking n empty.

For hmtx eligibility, I would prefer we don't check it's lsb of an empty
glyph at all (instead of requiring 0). That is, write something like:
 "...MUST check that leftSideBearing values match the xMin values of the
glyph bounding box for every *non-empty *glyph in a font"

We might also consider ignoring the lsb value for the degenerate non-empty
glyph with numContours == 0 as it's basically a poor encoding of an empty
glyph as far as I can tell.

Cheers, Rod S

On Tue, Jan 19, 2016 at 12:48 PM, Levantovsky, Vladimir <
Vladimir.Levantovsky@monotype.com> wrote:

> Folks,
>
>
>
> Per action 194 I made the following changes in the WOFF2 spec [1]:
>
> -          Handling of the empty glyph records in glyph table transform:
> instead of requiring a decoder to create an empty glyph record with no
> contours and zeroed-out bbox we should rather handle this by simply
> omitting the glyph record and creating a new entry in the loca table with
> the offset pointing to the previously created [last] glyph record so that
> loca[n] = loca[n-1];
>
> -          Added new conformance case for AT [2]: mustClearEmptyBBox –
> needs test description!
>
> -          Eliminated the DC conformance case mustCalculateEmptyBBox;
>
> -          Changed UA [3] conformance case mustRejectNonEmptyBBox – now
> set to unconditionally reject a font that has explicitly encoded bbox of an
> empty glyph. The existing test description seem to be fine, needs review!
>
> -          Special case handling for empty glyph records in hmtx
> transform (action 194): in order to confirm hmtx transform eligibility
> check that lsb of an empty glyph is equal to zero.
>
>
>
> Let’s review and discuss it tomorrow during our telcon.
>
>
>
> Thank you,
>
> Vlad
>
>
>
> [1] http://dev.w3.org/webfonts/WOFF2/spec/
>
> [2]
> https://www.w3.org/Fonts/WG/wiki/TestPlan20-AuthoringTool#Testable_Assertions
>
> [3]
> https://www.w3.org/Fonts/WG/wiki/TestPlan20-UserAgent#mustRejectNonEmptyBBox
>
>
>